Attribute for <TEXTAREA ...>onChange = "script command(s)"

Usage Recommendation

use it, but don't rely on it

onChange is triggered when the user changes the value of the text area.
It occurs after the user moves the cursor out of the field, not
while the user types. If you want to run a script for every key press you may want
to look at onKeyPress.

onChange can be used to modify the value of the text area after the users fills out the field. For example, suppose we want reset the field to completely upper
case. First we would put a script like the following into the
<HEAD> section of the page:

Notice that the one argument for the script is this, meaning that the field passes itself as the argument. This gives us the following form. Type something into the text area, then click in the next field.